Nampt, also known as visfatin or pre-B cell colony enhancer factor (PBEF), is a protein indispensable for the life activities of mammalians that is widely distributed in various tissues, particularly in adipose tissue, liver, muscle and bone marrow of human.
At present, Nampt is considered to have mainly the following 3 functions. 1. Nampt functions to have an enzyme activity, by which nicotinamide and 5′-phosphoribosyl-1′-pyrophosphate (PRPP) are catalyzed to convert into nicotinamide mononucleotide (NMN) and pyrophosphate, and NMN is then catalytically converted, by nicotinamide mononucleotide adenylyltransferase (Nmnat), into nicotinamide adenine dinucleotide (NAD), a energy substance essential to the cells. 80% of NAD in the mammalian cells is synthesized through this biosynthetic pathway, and Nampt is the rate limiting enzyme of the pathway, thus regulating the intracellular level of NAD. 2. Nampt functions as a pre-B cell colony enhancer factor (PBEF) secreted by lymphocytes, which stimulates the formation of B cell precursors in the presence of interleukin-7 (IL-7) and stem cell factor (SCF). 3. Nampt functions as an adipokine secreted by adipose cells and is involved in various biological functions. In 2005, Fukuhara et al. found that Nampt can activate the insulin receptor signaling by direct interaction with the insulin receptor. Since Nampt is highly expressed in visceral adipocytes, it is referred to as Visfatin.
With the increasing insight into the medicinal and health care effects of NMN, the market demand for NMN grows increasingly. The most environmentally friendly and pollution free method for producing NMN is a biocatalytic method in which nicotinamide and 5′-phosphoribosyl-1′-pyrophosphate (PRPP) are catalytically converted into NMN by Nampt. However, due to the low enzyme activity of the existing wild-type Nampt, the yield is low when Nampt is used in large-scale industrial catalytic production of NMN. As a result, the production cost is high, and the product is less competitive in the market, which severely restrict the industrial application of the biocatalytic production technology of NMN
Therefore, increasing the catalytic activity of Nampt is a key factor in reducing the biocatalytic synthesis cost of NMN, increasing the industrial application value of Nampt, and promoting the application of biocatalytic technology in industrial production of NMN.